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Susan Kane Driscoll and Charles Menzie Exponent August 4, 2014
Sediment Bioavailability Initiative (SBI): Development of Standard Methods and Approaches for the Use of Passive Samplers in Assessment and Management of Contaminated Sediment
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Problem Statement
§ Bioavailability of chemicals in sediment is recognized as a critical aspect for exposure, risk, and management
§ Passive sampler methods (PSMs) can be used to measure concentrations of freely dissolved contaminants (Cfree), which is a useful predictor of bioavailability
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PSMs are Better Predictor of Bioavailability for 3 Key Exposure Pathways
1. Direct exposure to invertebrates (toxicity, bioaccumulation)
2. Flux from sediments to overlying water column
3. Exposures in water column
Sediment layer 1
Sediment layer 2
Water column
Contaminant flux (CF)
CF
CF CF
CF
DDT
DDT DDT
DDT
DDT
DDT
ParticulatePhase
DissolvedPhase
DDT
DDT
Ex-situ or in-situ application of PSMs to measure Cfree relative to these pathways will reduce uncertainty in risk assessment and
subsequent risk management decisions
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DGT
Passive Sampling Phase or Media Configuration Target Analytes
Polydimethylsiloxane (PDMS) Coated fiber, vial HOCs
Polyethylene (PE) Film/sheet, tube HOCs
Polyoxymethylene (POM) Film/sheet HOCs
Ethylvinylacetate (EVA) Coated vial HOCs
Silicone rubber (SR) Sheet, Ring HOCs
Gels (e.g., DGT) Thin film “DGT” Metals
Resin impregnated polyacrylamide gel “Gellyfish” Metals
Metal-chelating media Disk/membrane Metals
Water-filled equilibration cell “Peeper” Metals
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Problem Statement …So why aren’t passive samplers more widely used?
§ Key barriers to regulatory acceptance and use include: – Failure of practitioners and decision makers to understand the
advantages and limitations of these chemical-based approaches over traditional analytical methods
– Confusion regarding the plethora of different methods and formats that are increasingly reported in the literature
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Problem Statement …So why aren’t passive samplers more widely used?
§ Key barriers to regulatory acceptance and use include: – Failure of practitioners and decision makers to understand the
advantages and limitations of these chemical-based approaches over traditional analytical methods
– Confusion regarding the plethora of different methods and formats that are increasingly reported in the literature
§ Lack of: – Technical guidance for PSM selection and standard methods – Use in regulatory decision-making contexts
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Problem Statement …So why aren’t passive samplers more widely used?
§ Key barriers to regulatory acceptance and use include: – Failure of practitioners and decision makers to understand the
advantages and limitations of these chemical-based approaches over traditional analytical methods
– Confusion regarding the plethora of different methods and formats that are increasingly reported in the literature
§ Lack of: – Technical guidance for PSM selection and standard methods – Use in regulatory decision-making contexts
§ Limited experience in use and analysis by commercial laboratories and site managers
§ Uncertainty over cost versus benefit
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Problem Statement …So why aren’t passive samplers more widely used?
§ “A big barrier to use is that the methods are not standardized (i.e., EPA or ASTM), and that there are not a number of accredited commercial labs doing this work. End users do not want to go to the universities to have this done; there needs to be a method that is “off-the-shelf”, has appropriate QA/QC, and that can produce comparable numbers across the different laboratories. Without a “price” and a “part number”, acceptance will be limited.”
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Problem Statement (continued)
There is a need to move from insights, research, and general guidance to
specific guidelines and actions
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SETAC Pellston Workshop —Technical Guidance on Bioavailability Measurements using Passive Sampling Methods for Management of Contaminated Sediments. 7–9 November, 2012 Costa Mesa, CA
5 papers published in IEAM – State of the Science for
Organic Contaminants – State of the Science for
Metals § Summarize literature; types and
uses of PSMs in sediment – Scientific Rationale
Supporting Use of Freely Dissolved Concentrations § Articulate technical basis for
advancing use of PSMs as a bioavailability-based LOE in investigations and decisions
– Practical Guidance for Selection, Calibration and Implementation § Provide practical technical
guidance for laboratory and field deployment of PSMs (method selection, standardization, QA)
– Risk Assessment and Management § Define current and future
management applications; identify communication needs for PSMs in decision contexts; identify research needs
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User’s Manual
– Introduction – Sampler-specific sections
on POM, PDMS and LDPE § Introduction § Laboratory Applications § Field Applications § Data Analysis
– Evaluation of Equilibrium and Use of PRCs
– Extraction and
Instrumental Analysis § Standard Procedures § Detection Limits
– QA/QC § Accuracy and Precision
– Appendix: Provisional Partition Coefficients
§ Joint EPA/SERDP/ESTCP publication with focus on organic contaminants:
�
Laboratory, Field and Analytical Procedures for the Use of Passive
Samplers in the Evaluation of Contaminated Sediments: User’s
Manual
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Practices Manual
§ Based on 5 key guiding principles for selection, preparation, implementation and validation of PSMs
1. Define question(s) posed by managers to be addressed by measurement of Cfree using PSMs
Endpoints addressed by PSMs
§ Sediment toxicity § Benthic organism bioaccumulation § Transport, i.e., direction of flux, gradients § Spatial extent delineation § Site-specific Koc
§ Model calibration/verification
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Practices Manual (continued)
2. Determine pros/ cons of ex-situ (bring sediment sample back to lab) versus in-situ application of PSMs
Other considerations
§ Site accessibility/security § Time/cost § Level of expertise required § Regulatory considerations § Importance of spatial resolution
(heterogeneity; grab versus fine scale) § Temporal resolution
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3. Perform trade-off of key considerations to select the most appropriate PSM(s)
Technical considerations
§ Target analytes (magnitude of Kow, organic/inorganic)
§ Physicochemical parameters § Time for deployment § Performance specifications (sensitivity,
accuracy, precision) § Commercial availability
Practices Manual (continued)
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4. Establish QA/QC guidelines for project
§ Selection and use of appropriate pre-calibration parameters (e.g., Kpw values and potential temperature/salinity corrections)
§ Provisions to ensure attainment of equilibrium, or alternatively, for correction to an equilibrium condition
Practices Manual (continued)
NE
Time
Cp
NE = Non-Equilibrium Sampling (linear uptake phase)
E = Equilibrium Sampling (steady-state phase)
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5. Quantify PSM measurement uncertainty and propagate through the assessment
PSMs uses in sediment assessments and decision frameworks
§ Nature and extent § Flux measurements § Evaluating remedial options § Exposure and risk assessment § Use in tiered assessment approaches
Practices Manual (continued)
Our current understanding of uncertainty associated with Cfree measurement using PSMs is expected to be only a fraction of the uncertainty
associated with the status quo
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Case Studies Demonstrate Value for Site Management • Lake Cochituate, MA—PCBs, PE, Nature and extent • Grasse River, NY—PCBs, POM, Post remediation monitoring • Maryland Rivers—PCBs, POM, Surface water screening § Bailey’s Creek and Canal Creek, VA—PCBs, POM, Post
remediation monitoring § Anacostia River , Washington DC—PAHs, PDMS, Post
remediation monitoring/bioaccumulation (capping) § Naval Station San Diego, San Diego Bay, CA—PAHs, PDMS,
Assessment/bioaccumulation § Elliott Bay, WA—PAHs, PDMS, Post remediation monitoring § Hunters Point Naval Shipyard, San Francisco Bay, CA—PCBs,
PDMS, Bioaccumulation/post remedy monitoring (activated carbon) 18
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Case Studies Demonstrate Value for Site Management § Pensacola Harbor, FL —PAHs, PDMS, Assessment/bioaccumulation § McCormick and Baxter Portland Harbor Site, Portland, OR—PAHs, PDMS, Post remedy
monitoring (capping) § Tennessee Products, Chattanooga, TN—PAHs, PDMS, Post remedy monitoring (capping) § Pacific Sound Resources, Seattle, WA—PAHs, PDMS, Post remedy monitoring (capping) § Wyckoff/Eagle Harbor Site (Bainbridge Island, WA) —PAHs, PDMS, Post remedy
monitoring (capping) § San Jacinto River Waste Pits (Baytown, TX) —Dioxins, PDMS, Post remedy monitoring
(capping) § Roxana Marsh, Hammond, IN—PAHs, PDMS, Post remedy monitoring (capping) § Potrero Power Plant Site, San Francisco, CA—PAHs, PDMS, Assessment/
bioaccumulation § Quantico Marine Base (Quantico, VA)—DDX, PDMS, Assessment/bioaccumulation § Port Forchon, LA —PAHs, PDMS, Assessment § Bay Jimmy, Barataria Bay, LA—PAHs, PDMS, Assessment
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Case Study: Lake Cochicuate § Pore water concentrations (ng/L) for PCB congeners:
1. Porewater concentrations estimated from sediment concentrations average 20x higher than concentrations measured with PE
2. Hotspot identified in additional areas of high chemical activity
Measured PE data (CPE/KPEw)
versus Estimated used sediment data (Csed/focKoc)
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Risk Management Applications
§ Improvements to management applications utilizing Cfree determinations and data include: – Ambient or compliance monitoring programs – Identifying contaminant sources – Develop exposure-response relationships (e.g., sediment
toxicity tests) for use in development of cleanup goals – Understanding of risk zones based on likelihood of effects
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Risk Management Applications (continued)
§ Improvements to management applications utilizing Cfree determinations and data include: – Modeling (input parameters or verification data) – Evaluating remedial options and designs – Short- and long-term monitoring of chemical bioavailability – Evaluating results of sediment treatment, disposal, or
beneficial reuse following management actions – Evaluating remedy effectiveness
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Cost Assessment
Cost Element
Ponar Grab Sampling
Cost PE Sampling
Cost % Difference
Expendable Items $169 $37 128% Non-Expendable Items $960 $948 1% Field Labor $1,530 $1,240 21% Sample Shipment $243 $104 80% Total Field Cost $2,902 $2,330 22%
Total Analytical Cost $10,080 $11,022 -9%
Totals $12,982 $13,352 -3%
12 Ponar Grab sampling versus 12 PE sampling
Note: Cost assessment from Dr. P. Gschwend assumes contract lab charges same for PE analysis as sediment analysis.
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Questions?